The present invention relates to an apparatus for controlling an automobile engine, and more particularly to an apparatus for interconnecting a plurality of engine control systems by serial data transmission.
As automobile controls become more sophisticated, the volume of signal communications between them and the number of sensors and actuators increase. As a result, the number of couplings among control apparatuses increases. One method which has been developed to reduce the wiring requirement for interconnection of engine controls and actuators is to provide for serial data transmission by means of input/output (I/O) units which are separate from the central control unit. For example, in Japanese Patent Application Laid-Open No. 4-203344, necessary data is transmitted to and from control units such as an engine control unit and a transmission control unit, serially by microcomputer programs, according to predetermined transmission procedures. It is thus possible to transmit data serially to two separate control units by using respective microcomputers. However, since each control unit has its own microcomputer for the purpose of processing parallel-serial transmission of information multiple microcomputers are used for the same control function, and the required amount of hardware and software increases.
Moreover, in the aforementioned serial transmission arrangement, the drive interface for the ignition coil of the engine control apparatus and for the fuel injection valve is provided as a separate I/O unit. Thus, when such serial data transmission is utilized, a failure of the transmission line, such as a disconnection of an optical fiber or a faulty electrical contact, interrupts the transmission of signals from the control unit, and the automobile is no longer operable.